This invention pertains to drum-type brakes, and more particularly to drum-type brakes which incorporate a manually operable brake adjuster mechanism.
Drum-type brakes continue in extensive use on utility vehicles, particularly on utility trailers, mobile homes and boat trailers. Such drum brakes include electrical actuation, hydraulic surge-hitch actuators, pneumatic or mechanical actuators, or combinations or hybrids of these. Typically, an extensible mechanical adjuster is fitted between the adjacent non-actuated ends of the brake shoes. These ends are coupled by a tension spring against the adjuster, and the adjuster controls the running clearance between the brake shoes and the brake drums.
The adjuster commonly employs an adjustable component in the form of a rotatable notched or star wheel. This wheel is accessible through a plugged or stoppered opening formed in the brake backing plate, so that rotation in a given direction causes the running clearance to be reduced between the friction material on the brake shoe and the inside cylindrical braking surface of the drum.
Safe brake operation requires periodic manual brake adjustments to maintain proper brake operation and enhance vehicle safety. When the mechanical adjuster is not properly adjusted from time to time, the available brake actuation, such as by an electromagnet torque arm or hydraulic piston, can exceed the available stroke of the actuator and the brake will become unsafe or inoperative. The existing arrangements require that such manual adjustment be accessed by inserting a tool through the access hole formed in the backing plate. These arrangements have proved to be an inconvenience, a potential safety hazard, and a deterrent to brake maintenance.
There is the inconvenience of having to go beneath a vehicle for the purpose of adjusting the brakes, and this inconvenience results in fewer brake adjustments. Since it is necessary to jack the vehicle off the pavement or put it on a lift prior to adjustment, this condition presents the hazard of having to go under or reach under a vehicle which is so supported and work on the brakes from that position. Also, since owners and users often improvise their own brake maintenance, the risk of injury due to the unsafe operation of jacking equipment is real.
A large number of utility trailers and other vehicles which use manually adjustable brakes are built with drop spindles. A drop spindle is an axle which has a spindle portion which is elevated with respect to a transaxle portion, for the purpose of lowering the trailer frame and springs to a lower center of gravity. An example of an offset or drop spindle is shown in the Foster U.S. Pat. No. 4,127,306.
The spindle offset together with the closely surrounding frame of the vehicle substantially block access to the brake adjusting access hole conventionally formed in the backing plate. This lack of clear access is a further deterrent to one contemplating the adjustment of such brakes, and makes more difficult and dangerous the act of working underneath such a vehicle which has been jacked up or elevated for the purpose of brake adjustment.
There is therefore a need to provide a brake adjustment feature which is move readily accessible, both to trailer owners and to professionals, to encourage more frequent maintenance and provide less hazardous brake adjustment procedures. At the same time, such an improved access can provide improved visibility to enable accurate adjustments in less time.